6
MICRO-ORGANISMS AND DISEASES
What we have learned earlier Micro organisms cause contagious diseases. Tooth decay is caused by the lactic acid produced by bacteria living on the food remnants. Some micro-organisms, toxic substances, alcohol etc cause diseases which affect the liver. Certain diseases affect the respiratory system. They can be controlled and cured. The infection of micro-organism is a cause for diseases in joints.
99
BIOLOGY
There are several diseases which affect man. Some of them are transmissible and
Type of
Shape
Diseases
bacteria
others are not. The transmissible diseases are
pneumonia
called contagious diseases. Louis Pasteur discovered that the contagious diseases are caused by the entry of micro-organisms from
Coccus
eye cysts
the surrounding into the body. This discovery helped a lot in the understanding of diseases,
throat infection
to improve methods of treatment and to control the diseases effectively. The tuberculosis
discovery of antibiotics also led to a greater advancement in the modalities of treatment. Bacillus
tetanus
Do you know how pathogens enter the body and how the body reacts to them? It will be quite useful to know about some of
typhoid
the disease causing organisms or pathogens, the disease caused by them and the preventive measures against them.
Bacteria
siphilis Spirillum
The bacteria are of different types.
cholera
Observe table 6a. Understand the shape of different types of bacteria and the diseases caused by them.
Table 6.a Certain types of bacteria and the diseases caused by them
z
How does each type differ in its shape?
z
Have you seen diversity in the shape of
move through liquid medium using certain
similar types?
hairy appendages. Others have slimy outer
You know that we cannot see bacteria
covering which gives them protection.
with our naked eye. Let us examine their other characteristics. Some bacteria can
100
Don't you know that the bacteria reproduce by binary fission.
MICRO ORGANISMS AND DISEASES
During favourable conditions it takes
Bacteria which have better
only about twenty minutes for a bacterium to
surviving ability
divide once.
Some halophilic bacteria can live in
If so, how many bacteria will be formed
concentrated salt solution. Some other
from a single one in one day? What will
bacteria can live at a temperature of
happen if conditions are unfavourable?
110oC. They prepare ATP molecules
Observe the figure given below. (6.1.a,6.1.b)
by directly absorbing sunlight but they
How do bacteria overcome the
have no ability for photosynthesis.
unfavourable situations? How does their
Thermoacidophilic bacteria can live at
mode of reproduction differ with respect to
80o C and can survive upto acidic pH2.
the situations? Record the conclusions in
They can be seen in hot springs.
your science diary. Unfavourable situation cytoplasm outer covering
endospores
Figure 6.1.a Endospores are formed from the cytoplasm
Favourable situation
endospore
endospore grows
new bacterias formed and divides
Figure 6.1.b Division of endospores
Temperature is the major factor which
z
affects the multiplication of bacteria. What would be the nature of their multiplication at different temperatures? Analyse the figure
How far does our body temperature help the multiplication of bacteria?
z
What happens to the bacteria and endospores on heating?
6.2.
101
BIOLOGY
0
C
boiling point 1000
0
F
2120 bacteria are destroyed when we heat them under this temperatrue for adequate time. More bacteria are destroyed by overheating but not the endosperes.
62.80
1450
400 37.70
1040
body temperature 370
98.60
melting point
1000
36.10
970
150
590
7.20
450
00
320
bacteria slowly increase in numbers bacteria increase in number bacteria increase in number rapidly
bacteria increase in number bacteria increase in number slowly At this temperature the increase in number of bacteria stops, but will not be destroyed.
00
Figure 6.2 Influence of temperature on the multiplication of bacteria
z
When substances are taken out of the
temperature for about fifteen minutes. You
refrigerator, what will happen to the
can imagine why autoclaves are used in
bacteria in them?
hospitals to make the surgical instruments
Record the conclusions in the science
germ free. We get the same result when we
diary.
use the pressure cooker for cooking.
Now you know that endospores can
The micro-organisms like bacteria enter
survive the temperature of even boiling water.
our body, after overcoming several
In order to destroy the endospores they
unfavourable situations. What would happen,
should be heated under high pressure and
once they enter our body?
102
MICRO ORGANISMS AND DISEASES
You have seen that our body
understand why this occurs. This is a type
temperature is very suitable for the
of resistance activity . Our body resists
multiplication of bacteria. A lot of waste
against several diseases like this.
materials are deposited in our body as a result of the life processes of these microbes. These are called toxins. Toxins upset the life processes in our body. Sometimes it may destroy the cells too. The temperature of our body raises to make them inactive or to check their multiplication. Rise in body temperature is the first symptom of typhoid. Now you can
Bacteria cause several diseases besides typhoid. Haven't you understood about tuberculosis. This disease is caused by Mycobacterium tuberculosis. Does tuberculosis affect the lungs only? Observe the figure 6.3. Which are the other parts of the body affected by this disease? Prepare notes on that.
central nervous system Eye lymph node
pericardium
adrenal gland kidney
alimentary canal
bone and joints reproductive organs
bone marrow
skin
Figure 6.3 Sites of affection of tuberculosis other than lungs
103
BIOLOGY
Disease
Pathogen
Leptospirosis (Rat fever)
Leptospira ictero haemorrhagiae
Vibrio cholerae
Cholera
Tetanus
Clostridium tetani
Mycobacterium leprae
Leprosy
Mode of infection
Symptoms/Other characteristics
Through contaminated food and water, insects like housefly and untidy surroundings
Continuous diarrhoea, vomiting, over tiredness, muscle cramps, dehydration and loss of minerals. If this continues death may occur.
The germs seen in the urine of rat or water may enter into the human body through cuts or wounds on the skin. Through domestic animals, squirrel, rabbit etc. Through continuous contact with the patient
Headache, fever, shivering, body pain, redness of eyes, difficulty to look on sunlight, jaundice. It may affect the organs such as liver, kidney, lungs etc and lead to a severe condition.
From soil, animal excreta, dirty objects, unsterilised instruments. Through wounds
The body will curve like a bow due to sparm and rigidity of muscle. The disease is known as lock jaw because of the difficulty to open mouth. Death may occur due to the constant damage to the central nervous system.
The symptoms may not be seen from 3 to 5 years. Sensation of skin diminishes – rashes will appear, wounds in the fingers and loss of wounded part, swellings appear on the face, saddle nose etc.
Things to be taken care of Dilute rice soup with salt to be given at intervals. Provide medical help at once. Eradication of rats. Take medical help in time.
Seek medical help at the initial stages. By delaying treatment, though the disease can be cured, the bodily deformities still persist. Vaccination should be given
Table 6.b Some diseases caused by bacteria
Do you know the other diseases caused by bacteria? Observe the table 6.b.
Useful Bacteria There are thousands of different strains
Find out more diseases caused by
of bacteria all around the air, in water
bacteria and make a list of them in the
and in soil. Most of the bacteria are
science diary. Bacteria also cause food
useful. They decompose the organic
poisoning.
wastes, produce certain vitamins in the
Bacteria and Food poisoning
body of animals, help in digestion, change milk to curd, ferment grapes to
Bacteria such as Salmonella,
wine, and are used in the preparation
Staphylococcus, Clostridium botulinum
of antibiotics and hormones. Only a
etc poison the food materials.
small group of bacteria is harmful.
104
MICRO ORGANISMS AND DISEASES
Vomiting, diarrhoea abdominal pain and headache are the common symptoms
What is their structure? Observe the figure 6.4.
of food poisoning. Bacteria such as salmonella,
nucleic acid
o
staphylococcus etc are destroyed at 55 C.
protein coating
They are infected mainly through meat & other non-vegetarian food items. What are the precautions to be taken against
Figure 6.4 A typical virus
infection from these? Clostridium botulinum is a type of bacteria that grow in tinned meat (tinned
Observe the figure 6.5 and understand the diversity among viruses.
food). It produces a poison, botulin which causes the deadly food poisoning called botulism. This bacteria grow at about 43 o- 47 oC. It is an anaerobic bacteria. The endospores of this cannot be destroyed even by boiling.
Viruses Yo u h a v e r e a l i s e d h o w t h e multiplication of bacteria causes diseases. The viruses are another type of microorganisms and like bacteria they also cause diseases. At present they are a real threat
Figure 6.5 Different types of viruses
to the life of man. Viruses cause a variety of diseases from common cold to AIDS. You have learnt that the viruses show
Try to understand how the viruses
characteristics of life only when they are
multiply after getting entry into a host cell.
inside living cells but shows non-living
(Fig 6.6).
attributes when they are outside.
105
BIOLOGY
When the virus particles are formed
Rickettsia Rickettsia are micro-organisms smaller than bacteria and larger than viruses.
in the host cell, the membrane system of the cell gets damaged. Membrane damage
They have close resemblance with
causes rupture of lysosomes and release
bacteria in structure. Rickettsia cause
of lysosomal enzymes. Life processes get
diseases such as Rockie mountain
disrupted and the cell disintegrates. The
spotted
Q-fever.
viruses continue multiplying and cause
Rickettsia are spread through wounds,
damage to more and more cells. This leads
fleas, lice, bugs, food and air.
to a state of disease.
fever,
typhus,
SARS -A New Threat
protein coating nucleic acid
SARS
(Severe
Acute
Respiratory Syndrome) is a severe respiratory disease. It virus stick on to the host cell
was first reported from the south east region mainly from China. The causative organism is considered to be
inject nucleic acids in to the cell
a virus. The disease starts like a flu, then changes to pneumonia
and
severe
respiratory problems which nucleic acids multiplies in the cells
may lead to death. Acute fever, dry cough, respiratory trouble etc are the common symptoms. But sometimes
synthesize protein coating
headache, sprain, diarrohea etc may be found. Infection of this disease is through close
new viruses are formed by joining protein coating and nucleic acids
contact
with
the
patient. Which are the other viral diseases
viruses are coming out by bursting out of the host cell membrane. Figure 6.6 Reproduction of viruses
106
besides AIDS? Check the table 6.c and understand more facts about some of them.
MICRO ORGANISMS AND DISEASES
Disease
Causative organism
Mode of infection
Symptoms/Other characteristics
Things to be taken care of
Dengue fever
Dengue viruses
A type of mosquito by the name Aedes aegypti
Sudden and severe fever, severe headache, pain behind the eye balls, loss of appetite, red rashes on the face and chest, nausea. At severe stages there may be sudden fall in the number of blood platelets.
Treatment should start at the initial stages. Severity may cause death. Control of mosquitoes essential
Polio myelitis
Polio virus
Infection through food, water etc.
Fever, headache and weakness of hands and legs. Permanently handicapped due to damage of nerve cells to muscles
Polio drops (oral) should be given in time
Japanese encephalitis
Virus
Through culex mosquito
Severe fever, headache, nausea, vomiting. Difficulty in bending the neck, hallucination, muscle cramps, fainting.
Treatment should be given at the initial stages. Eradication of mosquitoes.
Figure 6.c Some diseases caused by the viruses
Protozoa
Pseudopodia, flagella, cilia etc help
Don't you know about the unicellular organisms called protozoa? Protozoa includes organisms such as amoeba. They differ from the bacteria in having a specific nucleus. Observe picture 6.7 and study the characteristics of protozoa. Prepare
protozoa in locomotion. You know how amoeba reproduces. The protozoa also multiplies through binary fission. How do they overcome the unfavourable situations?
notes in the science diary. nucleus pseudopodia
cilia
nucleus
flagella
nueleus Figure 6.7
Different types of Protozoa 107
BIOLOGY
Pathogenic Protozoa (Disease causing protozoa)
z
Severe fever
z
Chilling and shivering
Some protozoa cause diseases just like bacteria and virus. Dysentery, malarial fever etc are such diseases caused by protozoa.
z
Severe headache
z
Feeling of intense heat in the body
z
Symptoms repeat intermittently
Dysentery Dysentery is a disease caused by infection of small intestine. What are its symptoms?
Disease may gradually affect organs such as the brain and the kidneys, and become fatal. Therefore if fever with shivering develops, blood testing should be conducted to confirm whether it is malaria or not. The
z
Stomach ache
treatment should be taken for the period as
z
Frequent bowel movement
per the doctor’s advice.
z
Blood and mucous in stool
Black water fever
The causative organism is Entamoeba histolytica. How do the infective form of the germs that come out along with the faeces of the patient infect others?
Four different types of plasmodium such
Dysentery causes dehydration and loss of minerals. If no treatment is given in time it may affect the functioning of kidneys and sometimes it may lead to death. Do not stop the treatment even if the symptoms disappear. Complete eradication of the cysts of pathogens can be made possible only through long term treatment. Bacteria also cause dysentery.
pathogens grow and divide in our red
Malaria Malaria spreads through the bite of Anopheles mosquitoes. The causative organism is the protozoan, Plasmodium. What are the symptoms of Malaria? 108
as Plasmodium vivax, Plasmodium malariae, Plasmodium falciparum and Plasmodium ovale cause malaria. Among these the malaria affected by P.falsiparum is the most dangerous. The blood cells and destroy them. The haemoglobin and bile pigments formed due to the destruction of red blood cells are excreted through urine. This makes the urine appear dark in colour. This acute stage called black water fever is associated with P.falciparum malaria.
Fungi Have you noticed black spots on the wet clothes. It is due to a type of fungus. Mould on the bread is also due to fungus. Observe the fungus affected portion of the bread through a microscope. Compare your
MICRO ORGANISMS AND DISEASES
observations with the figure given below.
Infection through body fluids
(6.8) Make notes on it and record it in the science diary.
Diseases may develop even when the body fluids of patient or carriers happen to
spores
mix with that of normal ones.
hyphae
Do you know how the body fluids mix?
Figure 6.8 mould on bread
The body of the fungi called mycelium is made up of long thread like structures
z
through blood transfusions
z
using unsterilised needles and syringes
z
through sexual contacts Sexual diseases are transmitted only
through sexual contacts with the infected person. Gonorrhoea, syphilis etc are examples of sexually transmitted diseases.
called hyphae. You have learnt that the fungus reproduces by spores.
Haven't you heard about the disease called AIDS (Acquired Immuno Deficiency
Afflotoxin is dangerous
Syndrome). The causative organism for this
Afflotoxin produced by the fungus
is the HIV (Human Immuno Deficiency
Aspergillus flavus is dangerous. If a high
Viruses) which attacks lymphocytes that play
dose of it reaches the body it may cause
a significant role in immunity. This disease is
lung cancer. Sometimes this fungus grows
transmitted through body fluids. This can be
on food grains.
transmitted from mother to foetus.
Are fungi pathogenic?
December 1 - World AIDS Day
Fungi cause several diseases. Have
Every year December 1 is observed as
you noticed white patches in between the
World AIDS day with a view to
fingers of dhobies. This is caused by a
making the people aware of the
fungus. Fungi cause patches on skin,
deadful disease, AIDs.
athletes foot, ringworm desease, corn disease etc. Some fungi cause food poisoning. The toxin produced by them sometimes lead to death.
What happens when human immuno viruses attack lymphocytes? Body
109
BIOLOGY
becomes susceptible to any disease. You
extracted from micro-organisms. Some
can imagine the consequences. What are
others are produced through chemical
the precautions that are to be taken to
processes. They destroy or make the
prevent such diseases?
microbes inactive. The examples for some
Now we have understood about some infectious diseases. You know that there are other infectious diseases also. What
antibiotics are given below. z
Penicillin
z
Ampicillin
z
Streptomycin
z
Oriomycin
are the important infectious diseases common in your locality? Make a study and prepare a project report.
Disinfectants and Antiseptics
The discovery of antibiotics helped in
You might have noticed that cleaning
the treatment and cure of contagious
lotions such as phenols are used to clean
diseases such as typhoid, tuberculosis etc.
the floor, table and other equipments in
There are many antibiotics in the market
hospitals, hotels, homes etc. What is its
which are useful against many contagious
purpose?
diseases.
Disinfectants are strong chemicals that
Though antibiotics are useful, some of
can destroy microorganisms. Phenol,
them have side effects also. Observe the
bleaching powder, lysol, formalin etc are
table 6 d.
examples. Antiseptics are the chemicals used to destroy microorganisms in the body surface. It includes ethyl alcohol, boric acid, potassium permanganate. Dettol, savlon etc which can be used as disinfectants and antiseptics in dilute form. Care should be taken to avoid mixing of disinfectants with food and wounds.
Antibiotics Antibiotics are antimicrobial substances which can be used internally as well as externally. Some of them are Figure 6.d Antibiotics and their side effects
110
MICRO ORGANISMS AND DISEASES
An incidental discovery
lysozyme in tears
In 1928, a Scottish bacteriologist by name
mucus in nostrils
Alexander Flemming was working in St.Mary’s Hospital in London. He cultured bacteria in an agar medium. Once he came to notice that some of the bacteria got
lysozyme in saliva mucus and cilia in trachea
destroyed due to some reaction. By careful observation it was found that a chemical
skin - outer covering
produced by a fungus Pencillium notatum was responsible for the destruction of bacteria. That chemical was pencillin-the first antibiotic. It has the ability to destroy many bacteria. It was first used in 1940. In 1945 Nobel prize for medicine was awarded to Alexander Flemming, H.W Flory and E.B Chain. Don’t you know that
HCl in gastric juice
mucus and enzymes in small intestine bacteria in large intestine
blood clot in wound
lysozyme in urine
lactic acid in vagina
the indiscriminative use of antibiotics is dangerous? Emergence of antibiotic resistant bacteria is a new problem in the
Figure 6.9 Safety measures in the body
field of treatment. z
Do you understand the antibiotics are harmful to us. Production of bacteria which can resists antibiotics is a new
the entry of pathogens into the body? z
You know that diseases occur while pathogens get entry into our body. Though there are millions of pathogens around us, we do not often get an attack of diseases. Why?
How does the body check the pathogens from entering through inspiring air?
problem in the field of medical science.
Safety Measures in the Body
Which is the major safety device to check
z
Where do you see lysozymes which have bacteriocidal property? Make note on different parts of our
body which protect us from the attack of pathogens and give a presentation.
Immune System
Observe the figure 6.9. Find out the
You have now understood the safety
answers to the questions and record it in
measures adopted by the body to prevent
the science diary.
the attack of pathogens? What would be 111
BIOLOGY
the result if this measures fail? The body resists against the disease germs in accordance with their mode of attack.
Notice the changes in affected part of blood vessels. z
What is the use of expansion of gaps on the blood capillaries?
z
Why do the affected parts swell and red coloured?
Have you noticed the appearance of swellings during trauma? Do you know that this also is a method of resistance. Observe the figure 6.10.
Swelling response in the affected area is local and provides immediate resistant
bacteria A
attack of bacteria
activity. You know that a type of white blood corpuscles called lymphocytes
blood capillaries
produce antibodies to resist the disease germs. When more lymphocytes are B
more blood comes out. Blood capillaries dilate. The gap between the walls of the capillareis increases.
needed, the lymph glands in the affected area do extra work to produce more lymphocytes. Such lymph glands also show swelling. That is why wounds are often associated with inflammation of lymph glands.
C
phagocytes coming through the crevices
Immunity You have understood that the human body has an innate power of immunity. Do you know how the body resists the disease germs, once they enter the body. Observe
D
phagocytes engulf the bacteria and destroy them
the Illustration I given below. You have understood why even after the attack of pathogens, we do not always get diseases. Some lymphocytes retain the ability
E
blood capillaries returns to original stage
to produce antibodies even after the body has recovered from the disease. The antibodies once produced will remain
Figure 6.10 Swelling responses in the affected area
112
MICRO ORGANISMS AND DISEASES
Antigens All the substances which body considers as foreign bodies Eg: Other protein molecules, Disease germs, Toxins etc.
↓
Quick response
Resistant response
Slow response
General for all antigens (Non-specific)
Phago cytosis
Safety measures in the body-skin, mucus membrane, lysozyme etc.
Special for entering antigens (Specific)
Swelling response
The lymphocytes or antibodies which they produce specifically, destroy or make - the antigens inactive. Illustration I
viable for a long period. You have heard
Health Organisations
that we develop permanent immunity
Have you heard about the World Health
against diseases such as chickenpox,
Organisation? It works with a view to
mumps etc once we happened to be
provide health for all in the world. It
victims of such diseases. Now you may
functions with the guidance of United
knows the reason.
Immunisation Prevention is always better than cure. You have seen that the children are given
Nations. Organisations like UNICEF, International Red Cross, Indian Red Cross Society etc functions in health and social welfare
fields.
There
are
different
organisations working in the national and international level.
April 7 is celebrated
preventive medicines. Do you know what
as World Health Day in remembrance of
are the preventive medicines?
that day in 1948, when all the member countries have signed when the constitution of World Health Organisation.
113
BIOLOGY
The killed or inactive disease germs,
to produce antibodies against a specific
inactivated toxins etc are given as
disease. The antibodies once produced
preventive medicines. These are called
will protect the body from the further
vaccines. They act as antigens which
attack germs of that specific disease.
stimulate the immune system of the body The begining of immunisation
The body does not get adequate time to produce antibodies against certain
An English doctor Edward Jenner
diseases such as cholera.
observed that small pox does not
situations, antibodies are directly injected
appear in persons who were once
to attain immunity.
attacked by the disease.
Jenner
injected the pus of small pox with a needle in to a girl from a girl having
In such
Immunisation is a method of giving vaccines inorder to resist the diseases.
the disease. After that the injected
Visit a nearby Primary Health Centre
person showed the symptems of disease
and understand the different vaccines given
and then got cured. After about two
for different diseases.
months he injected the pus of the
immunisation chart and exhibit.
disease from another patient in to the same girl. The girl did not show any symptoms of disease. This experiment in
1796
was
the
begining
of
immunisation. The term vaccination is derived from a Latin word 'vacca' which means cow. The immunisation is also called vaccination in the rememberance of Jenner's small pox injection. The material used for this is called vaccine.
114
Prepare an
MICRO ORGANISMS AND DISEASES
SUMMARY
There is a suitable environment in our body for the growth and multiplication of the microorganism.
Disinfectants, antiseptics, antibodies etc. help to destroy the microorganisms. Majority of antibiotics have side effects.
There are special adaptations for microorganisms to overcome the unfavourable situations.
The microrganism which cause the contagious diseases have different shape and structure.
Our body has a safety measure to prevent the entry of pathogens. When this measure fails, the disease manifests.
White blood corpuscles play an important role in destroying the pathogens that enter our body.
Through proper immunisation we can prevent many diseases. By taking adequate precautions, the diseases can be checked.
Some micro-organisms cause food poisoning.
Some diseases are transmitted through air, water, food and by some organisms.
Some pathogens are transmitted through body fluids.
FURTHER ACTIVITIES ¬
Explain how the microorganisms cause diseases.
¬
How can we avoid the fungal diseases affecting man?
¬
Some of the diseases which are considered to be under control pose new threats. Eg. Tuberculosis. What explanation would you give for this.
¬
“Carelessness may lead to death”check how far this statement is true in the case of contagious diseases.
¬
Explain the importance of immunisation.
¬
Prepare posters on the importance of cleanliness in controlling contagious diseases.
¬
The immediate treatment to diarrhoea is to control dehydration and loss of minerals. Which are the drinks that can be used for it? Which are the components in the ORS solution and at what proportions? Collect information.
¬
What all things would be planned to observe the December 1 as World AIDS Day? Prepare notes on it.
¬
Collect and Exhibit the pictures in the class of scientists who invented the different antibiotics.
115